1. Field of the Invention
The invention relates to a method for determining the temperature of a power semiconductor.
2. Description of the Related Art
Integrated semiconductor components are produced as so-called semiconductor chips, or chips for short, in general from a base substrate, e.g., a silicon wafer. Power semiconductors, e.g., IGBTs, are also produced as chips of this type.
A power semiconductor generally has a control contact, via which the power semiconductor is driven. In the case of an IGBT, for example, this is the gate, via which a switching operation is initiated in the IGBT. Power semiconductors with an integrated series resistor are known. The series resistor is then connected in series with the control contact within the power semiconductor.
In this case, the driving is still effected via the control contact. The internal gate resistor co-ordinated with the respective power semiconductor is intended, e.g., to compensate for differently formed or pronounced Miller plateaus and to bring about more uniform switching of the power semiconductor.
A more recent generation of power semiconductors is also known which have, alongside the first control contact mentioned, a second contact, i.e., there is a usually smaller contact window or so-called auxiliary window on the chip. This auxiliary window is in direct contact with the actual internal control contact or control connection in the power semiconductor and thereby bypasses the series resistor.
In other words, the resistor integrated in the chip is situated between the two control contacts. The first pole of the resistor is therefore connected to the first control contact, and its second pole is connected to the second control contact. The internal gate resistor has, under normal conditions, for example a resistance value of approximately 10Ω. Usually, only the contact window—designated as the main window—of the first control contact is ever bonded or contact-connected on such a chip. The series resistor itself is inaccessible for contact-connection since it is situated internally in the power semiconductor.
The service life of such a power semiconductor depends largely upon the temperature stress or the temperature loading experienced by the power semiconductor in the course of its operating. For this reason, the so-called junction temperature is crucial, primarily in power semiconductor switches. It is therefore desirable to track the junction temperature of a power semiconductor as accurately as possible during the operation of the power semiconductor; e.g., a rough estimation of the expected remaining service life of the chip thus becomes possible. Replacement can then take place in a timely and planned fashion before failure of the chip is expected.